Police said they were called to the Burgess Hill Inn, in Keymer Road, Burgess Hill, at 10.15pm to reports of an assault.
A police spokesman said: “Three masked men turned up to the pub and attacked a customer with baseball bats before making off from the scene.
“The victim, a 32-year-old local man, suffered head and leg injuries.
“He was taken to the Royal Sussex County Hospital in Brighton and has since been released.”
Police remain at the scene as they as they carry out forensics and gather further information about last night’s attack, the spokesman confirmed.
Police are appealing for anyone who saw what happened to contact them quoting serial 1486 of 03/08.